MICROGLIAL INTERLEUKIN-1-ALPHA EXPRESSION IN BRAIN-REGIONS IN ALZHEIMERS-DISEASE - CORRELATION WITH NEURITIC PLAQUE DISTRIBUTION

Interleukin-1 alpha-immunoreactive (IL-1 alpha(+)) microglia are promi nent components of neuritic plaques in Alzheimer's disease, and may be important in the evolution of neuritic plaques from diffuse amyloid d eposits. Neuritic plaques show a characteristic distribution across ce rebral regions and are absent in the cerebellum of patients with Alzhe imer's disease. We used single- and dual-immunohistochemical labelling to investigate the possibility that the expression of IL-1 alpha is c orrelated with this regional distribution of neuritic (tau 2-immunorea ctive, tau 2(+)) plaques. In Alzheimer's disease, tau 2(+) neuritic pl aques occurred with increasing frequency in grey matter of frontal and occipital lobes temporal lobe, and hippocampus. There were positive p rominent components of neuritic plaques in correlations between the re gional patterns of distribution of activated IL-1 alpha(+) microglia a nd tau2(+) neuritic plaques as well as between activated IL-1 alpha(+) microglia and activated astrocytes. No activated lL-1 alpha(+) microg lia, tau 2(+) neuritic plaques, or activated astrocytes were observed in cerebellum of these Alzheimer patients. These regional relationship s between activated IL-1 alpha(+) microglia, tau 2(+) neuritic plaques , and activated astrocytes; together with the established functions of IL-1, support a causal association between the overexpression of IL-1 and the evolution of beta-amyloid deposits into neuritic plaques in A lzheimer's disease.